Workers in the art of handling and transporting items appreciate that, at times, an item is to be selectively advanced either at high speed, or at a relatively low speed (e.g. to pass a special processing station). If, as is common, the station needs "firing pulses" to synchronize with item travel, a firing means may advantageously provide this by tracking the document directly. But doing so will commonly involve a "power take-off" (e.g. where document motion is used to activate this) which, in turn, presents the problem of retarding the thing you are tracking.
This invention addresses this problem and provides "floating" pulse encoder means, together with "encoder engagement means adapted to accommodate varying document thickness and "balanced pressure means" to adjust document-engagement forces.
Such features and advantages are a salient object hereof.
Other objects and advantages of the present invention will be apparent to those skilled in the art.
A sheet transport array for advancing sheets along a track at a desired speed past a process station. A sheet (for example, a check) advances along a track and is decelerated to pass through a process station, for example an ink encoder. The sheet enters a drive roller assembly having a drive roller and a drive idler that decelerates the advancing sheet as it passes the process station. A second roller assembly includes at least a second roller and a second idler. The second idler moves at the higher speed of the advancing sheet. The second roller is still moving at the normal high document speed of the track but slips on the document that remains at the lowered speed. The document continues along the track toward a floating roller assembly including at least a floating roller and a floating idler, neither of which is driven. The floating idler is coupled by a belt to the second idler so as to move at the same speed as the second idler and hence the advancing sheet. The floating roller and floating idler have a pinch point with a pinch force such that the floating roller and floating idler move at the same speed as the advancing sheet.
Before the advancing sheet reaches the floating roller assembly the floating roller drives a speed measuring device at the speed of the advancing sheet. As the advancing sheet reaches the pinch point for the floating roller assembly the floating roller and floating idler are moving at the same speed as the advancing sheet and the advancing sheet is not slowed down. As the document enters the pinch point the advancing document takes over in driving the floating roller. The floating idler no longer controls the floating roller speed. This allows the advancing document to control the speed measuring device and hence signal to the process station. This is important because the size of the document may be such that the document has left the original slower drive roller and is accelerating. The speed measuring device, for example, may be an optical encoder that measures the speed of the advancing sheet and provides a control signal to an ink endorser process station to control the ink encoding on the advancing sheet.